Any given method for the analysis of semi-volatile total petroleum hydrocarbons (TPH, C10-C36) in contaminated soil is made up of a number of procedures, each of which may be subject to improvement ...or optimization. One such procedure involves the extraction of TPH from soil samples using an appropriate solvent. A solvent that is widely used is dichloromethane (DCM). Ideally, the chosen solvent should represent the best compromise between factors such as cost, extraction efficiency and occupational health and safety concerns. We have initiated a search for alternatives to neat DCM which are equally efficient at solubilising TPH over a range of soil types, but which are less expensive to purchase and dispose of, and which are less toxic. Two studies were carried out involving the analysis of TPH levels in a total of 78 field samples, from a number of contaminated sites. For Study 1, TPH levels were determined for 36 samples (from five different sites), comparing the use of neat DCM versus 50%v/v DCM/acetone as extractant solvents. For Study 2, TPH levels were determined for 42 samples (from one site), comparing the use of 50%v/v DCM/acetone versus neat 2-propanol as extractant solvents. Apart from varying the extractant solvent, all other aspects of the method were kept constant. The soils were characterized for all samples, and the six sites were found to have similar moisture content and soil type distributions. Levels of TPH in the extracts were determined by gas chromatography with flame ionization detection (GC/FID) and, using the paired t-test, were statistically compared between each of the two pairs of extractant solvents used. These investigations suggest that for routine field samples, and for sites of the type represented here, 50%v/v DCM/acetone may be confidently substituted for neat DCM as an extractant solvent. However, 2-propanol is not recommended as a substitute for either 50% DCM/acetone or DCM.
Antioxidant measurement assays are widely used and should be chosen based on their being fit for purpose. Likewise, the mode of reporting antioxidant measurements should also be fit for purpose. The ...Oxygen Radical Absorbance Capacity (ORAC) assay is widely used internationally for measuring the antioxidant capacity of commodities using the peroxyl radical. However, the current mode of reporting of the ORAC values is not obvious, especially for the consumer groups. In this mode, reporting of the ORAC values is the unit of micromoles of vitamin E analogue (VEA), known commercially as Trolox Equivalents per kilogram or per litre (μMT.E./kg or L). Unlike mass units, molar units are not widely used in nutrition information panels (NIP). This paper presents a simple mathematical model for conversion of ORAC values to mass units to facilitate better understanding of the antioxidant capacity quoted. Additionally, mass values are in keeping with current labelling practice in Australia. Unless legislation is passed for the regulation of ORAC data use in labelling and product marketing, mass units should be considered as a mode of reporting, limiting sensationalism of antioxidant capacity and keeping with current labelling practice.
Environmental consultants and analytical laboratories are increasingly realizing the importance of analytical method selection and validation for the reliable measurement of soil contamination. ...Aromatic hydrocarbons (BTEX) is one class of environmentally significant soil contamination for which testing is required by regulatory authorities in most industrialized countries. Unfortunately, in most guidelines there is a lack of direction for the selection of a testing method for BTEX and, in practice, any one of a variety of methods may be employed. The fact that these may not all yield comparable results is a source of much frustration in the industry and there is a paucity of published research into this problem. In a number of carefully controlled experiments, the method dependency of measured BTEX levels in contaminated soil samples has been investigated. Three commonly employed methods, namely, (methanol extraction) purge-and-trap/gas chromatography with mass selective detection (P&T/GCMSD), headspace/GCMSD and dichloromethane (DCM) extraction/gas chromatography with flame ionization detection (GCFID) have been compared in the analysis of 109 gasoline-contaminated soil samples collected from station sites in Melbourne, Australia. Measurable BTEX concentrations were recorded in 92% of the samples using P&T/GCMSD, 59% using DCM/GCFID, and 40% using headspace/GCMSD. Correspondingly, the magnitudes of the recovered concentrations were significantly higher by P&T/GCMSD than by DCM/GCFID, which in turn were significantly higher than the magnitudes determined by headspace/GCMSD. These trends are evident for both clay and sandy soils. These studies clearly demonstrate that, for the three commonly employed methods described, measured BTEX levels are extraction and analytical method dependent in at least two different soil types.PUBLICATION ABSTRACT
Globally it is estimated that up to 37% of all marine mammals are at a risk of extinction, due in particular to human impacts, including coastal pollution. Dolphins are known to be at risk from ...anthropogenic contaminants due to their longevity and high trophic position. While it is known that beach-cast animals are often high in contaminants, it has not been possible to determine whether levels may also be high in live animals from the same populations. In this paper we quantitatively assess mercury contamination in the two main populations of a newly described dolphin species from south eastern Australia, Tursiops australis. This species appear to be limited to coastal waters in close proximity to a major urban centre, and as such is likely to be vulnerable to anthropogenic pollution. For the first time, we were able to compare blubber mercury concentrations from biopsy samples of live individuals and necropsies of beach-cast animals and show that beach-cast animals were highly contaminated with mercury, at almost three times the levels found in live animals. Levels in live animals were also high, and are attributable to chronic low dose exposure to mercury from the dolphin's diet. Measurable levels of mercury were found in a number of important prey fish species. This illustrates the potential for low dose toxins in the environment to pass through marine food webs and potentially contribute to marine mammal deaths. This study demonstrates the potential use of blubber from biopsy samples to make inferences about the health of dolphins exposed to mercury.
Field measurement of volatile petroleum hydrocarbon in soil usually precedes the submission of samples for more rigorous analysis in the laboratory. Hand-held photoionization detectors (HHPIDs) are ...commonly used for field measurements, although there is growing concern about their reliability under field conditions. This concern is accentuated by an increasing tendency to rely on such field measurements alone. Three different case studies, where commercial HHPID field data and the corresponding laboratory data have been made available to us, were critically examined. Disturbingly, there is little correlation between the HHPID readings obtained in the field and the corresponding measurements in the laboratory, with a large number of false positives being recorded. Also, the measurements obtained from the HHPID were invariably much higher than the corresponding laboratory measurements. In an attempt to identify some of the underlying problems that could influence the response of HHPIDs in the field, a series of laboratory experiments was conducted under controlled conditions in order to monitor, by Gas Chromatography with Mass Selective Detection (GCMSD), the linearity and accuracy of HHPID response to spiked BTEX levels (benzene, toluene, ethyl benzene and xylenes) in a variety of matrices under varying moisture content conditions (namely; in pure water, dry sandy loam, dry silt and moist silt). These studies reveal that, under controlled conditions, the HHPID response is linear over a spiked BTEX range of approximately 0-500mg/kg for a variety of matrices. However, the sensitivity (as measured by the slope of the response line) depends very much on the specific combination of conditions, such as the matrix and moisture content. These results suggest that for linearity of response to be established in the field, corrections must be made for variations in moisture content and soil type, and perhaps for other parameters. The slope of the response line could then be used as an "instrument factor" to quantify the level of contaminant from the HHPID response. Several other factors that could influence HHPID readings were also investigated including the HHPID response over time and the effect on response of component interactions in contaminant mixtures. The former investigation shows that there is no statistical difference between HHPID measurements taken up to 1.5h apart from identical spiked samples. The latter study suggests that multiple components in a sample may affect the HHPID response.
The contamination of soil due to the presence of petroleum hydrocarbons is an important environmental issue. In Australia, there are a number of methods that are employed for such analysis, all of ...which are widely accepted. In this study, we specifically focused on the sonication and the soxhlet extraction techniques, which are two of the common methods of extracting semi-volatile Total Petroleum Hydrocarbons (TPH). The components that fall within this fraction are the hydrocarbons with their carbon index number ranging between 10 and 36 (i.e. C10 to C36). The C10 to C36 TPH fraction was further broken up into sub-fractions, which were C10-C14, C15-C28 and C29-C36, in order that specific details regarding the extent of the contamination could be assessed. The TPH extractions were carried out on 84 homogenized clay soil samples collected from service station sites. The soils were then classified and confirmed to contain greater than 50% clay in all cases. The moisture content of the soil varied with a minimum of 6.9% and a maximum of 32.7%. These soils were extracted in duplicate by the sonication and the soxhlet extraction techniques. The extracts were analysed by gas chromatography with flame ionisation detection (GCFID). After performing the relevant statistical analysis it was concluded that the soxhlet extraction generated higher semi-volatile TPH concentrations than the sonication extraction technique for the clay soil samples. This variation was significant and therefore should be an important factor to consider since TPH analysis is mostly conducted using the sonication extraction technique.
A survey of environmental chemistry laboratory experiments published during the period 1969-2000 in the mainstream chemical education journals, The Journal of Chemical Education and Education in ...Chemistry, was conducted. The experiments were categorized as being related to the environmental domains of air, water, or soil. Using the same timeframe, a similar survey was carried out for commonly used environmental chemistry textbooks, assessing the relative number of pages devoted to the same areas. The data obtained from both analyses indicate that the area of soil is seriously underrepresented in the environmental chemistry educational literature. This suggests a need to develop more environmental chemistry educational material (in the form of published laboratory experiments and textbook material) related to soil chemistry and soil contamination. To provide a basis for optimizing the level of integration in the design of such experiments, the publications surveyed were categorized according to how they integrate the four traditional subfields of chemistry --organic, inorganic, physical, and analytical.
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